Vessels

While all agree that a hypophysio-porta, system exists in niammals, controversy still esists as to the direction of flow of the blood within the vessels and as to the extent of the portal system itself. Popa ('30a, '30b, '33, '37, '38) has always stoutly maintained that the arrangement serves to convey both blood and contained secretions from all parts of the hypophysis to the tuberal region of the hypothalamus and third ventricle. He has been supported in this by a number of workers, 'Espinasse ( '33), Basir ( '32)' Collin ('38) and others. On the other hand most America11 and British authors now appear to favor the conceptions of TYislocki and King ('36) and of Wislocki ('36, '37a, '37b, '38) that the direction of flow is toward the pars distalis and that the vessels contribute insignificant1;v or not at all to the neural lobe and hypothalamus. The portal vessels have been clescribed in detail in only a few species. These include among mammals man, the macaque and cat (TT'islocki, loc. cit.), dog, rabbit, rat, and guinea pig (Green and Harris, '47). Apart from the one short account of Houssay, Biassoti, and Saniinartino ( '35) for the toad, a portal system has been clearly described in only a few